textproduct: Rapid City

KEY MESSAGES

- Thunderstorms chances are diminishing but isolated strong gusts are still likely due to downsloping for a couple more hours.

- A cold front moves slowly through the area Sunday and Sunday night, bringing showers and thunderstorms, severe storms are possible.

UPDATE

Issued at 1053 PM MDT Sat Jun 6 2026

Storms have formed along a N-S oriented sfc trof over northeastern WY/far western SD. A few of these storms have intensified in the past hour or so but remain sub-severe. These storms will push across the Black Hills in the next few hours and thus have painted some light PoPs over Rapid City and western SD. Main threats with these storms will be gusty winds of 40-55 mph and small (<1") hail.

Attention then turns to tomorrow and the potential threat for severe weather across much of the forecast area. A potent upper level trof will push across the Northern Rockies through the day tomorrow as a sfc low deepens over MT/WY out over the Northern Plains and attendant cold front stalls out over NW SD into NE WY. Low level southeast flow will facilitate moisture advection into the region. By the afternoon and evening hours, ML CAPE values of 1500-3000 J/kg will overspread much of western SD and portions of NE WY. Current thinking is discrete storms will fire across northeastern WY along the stalled out front early in the afternoon. Increasing mid level flow, courtesy of the approaching trof, will support 0-6km shear of 40-50kt and supercell structure. These storms will be capable of large hail and damaging winds, though a brief tornado can't be ruled out. Limiting factor here would be warm 700 mb temps (14-16C) supporting a stout cap over much of northeastern WY. Better chances for storm development later on in the evening hours as the cold front pushes through and storms form into a line along the front. Damaging winds will be the main threat with these storms.

DISCUSSION

(This Evening Through Saturday) Issued at 110 PM MDT Sat Jun 6 2026

Upper level analysis has a shortwave ridge centered over the Eastern Dakotas with a low dropping into the Pacific Northwest. At the surface a cold front extends from northeastern Montana into southwestern Idaho, with a weak lee trof developing near the Bighorns. Visible satellite indicates a few mid level clouds ahead of the front with the lower portions of the UNR 18Z sounding showing very dry air off the surface.

For tonight, a high-based storm or two could get going over the Black Hills or northeastern Wyoming due to daytime heating and the forcing of the lee trof. Hi-res models are indicating a broken line of strong showers and storms along the trof, extending along the WY/SD border by 02Z-ish. With limited low-level moisture, the primary threat would be gusty winds.

The cold front approaches the area around 06Z tonight, reaching the SD/WY border near 12Z. From there, it is expected to stall- out. This stalled boundary will be the primary focus for convection during the afternoon and evening. Supercell development is possible with 0-6 km shear estimated to be 40-50 kts, steep lapse rates, MLCAPE of 1700 J/kg, and MUCAPE 2400 J/kg. With drier air still expected off the surface and dewpoints ranging from 35 to 55 degrees, expect LP supercells capable of producing significant hail and very strong winds. A tornado could also be possible.

Monday will be cooler behind the cold front, with highs only in the 70s and 80s. Surface high pressure will slide through the CWA, resulting in increasing southeasterly winds of 10-25 mph during the afternoon. Another hot day is ahead on Tuesday with prefrontal warming back into the 90s. Once again the NBM is probably running too, due to the greenness. A deep upper low and another cold front impact the area on Wednesday and Thursday, resulting in a chance for scattered storms.

AVIATION

(For the 06Z TAFS Through 06Z Sunday Night) Issued At 1155 PM MDT Sat Jun 6 2026

VFR conditions are generally expected through most of the forecast period. Isolated thunderstorm chances are diminishing but still seeing occasional wind gusts near 50 mph coming off the Black Hills.

Looking ahead, VFR conditions will persist with mainly wind speed and wind directions changes coming due to the expected front. Winds will swing from the south/southeast to the north/northwest when the front moves through. Thunderstorms will be likely with the front.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.